Design Rational for Total Ankle Arthroplasty: An Update.

The design of total ankle arthroplasty (TAA) systems is rapidly evolving as device companies try to keep pace with the expansion of surgical indications and a refinement of techniques for TAA. Even since the publication of the latest "update," published in 2018, three new designs and three updates on preexisting third-generation implants came onto the market. Improvements in third-generation TAA systems include minimal bone resection, retaining ligamentous support, and anatomic balancing. Fourth-generation systems use 3D printing technology, improved talus and tibia designs based on CT scans of arthritic and normal ankles, and include patient-specific instrumentation. We will then explore the short-term and mid-term outcomes of the previously discussed six TAA systems-INBONE, INFINITY, INVISION (Stryker), Salto-Talaris (Smith and Nephew), Scandinavian Total Ankle Arthroplasty (Enovis), Trabecular Metal Total Ankle (Zimmer Biomet), and VANTAGE (Exactech). As more research pours in regarding mid- to long-term outcomes of these implants, it is important to assess the design rationale and summarize current outcome data for these implants.